for building the binaries

If the authority waits until the next descriptor submission deadline,
it may miss retrieving the consensus made in the previous epoch and will
not have a copy of the previous consensus from which to inherit the
correct topology. This commit fixes this issue by returning to
stateBootstrap and retrying a consensus fetch for the current epoch.

Return ErrGone, there is no bootstrap for current epoch.

voting client now tries each Address in random order until a
successful connection is made.

Improve Makefile and travis file